105 TTRPG Dice + simple I2C peripheral

105 : TTRPG Dice + simple I2C peripheral

How it works

Press buttons to roll various types of TTRPG dice

Playing table top role playing games (TTRPGs) often involves rolling dice of various types. This design is a combination of the most common types of dice used.

It has six button inputs, each corresponding to a certain type of die, and a two-digit seven segment display that shows the result of the roll when the button is released.

While a button is pressed, a counter is decremented every clock cycle. When the counter reaches 1, it is reloaded with the largest value of the corresponding die. When the button is released, the counter stops and the result is displayed on the seven segment display. Around 8 seconds later, the display is turned off.

The design outputs seven segment signals and 'common' drivers for two digit displays. It has configuration pins that set the active level of segment and common signals independently of each other, to allow the connection of either common-cathode or common-anode diplays, or displays with inverting or non-inverting drive buffers for segments and/or common signals. Similarly, the button inputs can be configured as active low or high.

Dice up to d10 can use a single seven segment display without a common driver like the one on the demo board. If such a display is used, it will toggle between showing the 1s digit and the blanked 10s digit. When the result is 10, it will show a 1 and 0 superimposed, which will look like a slightly wonky 0.

The design uses clock timing to debounce the buttons and is optimized to run at 32768 Hz, but it should work well at frequencies from 10kHz to 100kHz. At higher frequencies, the button debouncer may be unreliable and display muxing may not work properly. At lower frequencies, the higher valued dice will have a low cycle rate and it could be possible to cheat by using well-timed key presses. The clock frequency will also affect the timer that turns off the display.

The 'polarity' config pins sets the active level for the corresponding I/O signals. For instance: uio[7]=0 causes the digit mux signals to be active low, suitable for directly driving common cathode pins. When uio[6]=1, lit segments are high, suitable for direct segment drive of common cathode displays. Similarly, when uio[5]=0 button inputs are expected to be high when idle and low when pressed.

How to test

Set clock frequency to 32768 Hz (10-100 kHz). Configure uio[7:5] for the appropriate signal polarity:

Seven segment uio[7:6]
Common cathode, direct segment drive (demo board) 01
Common anode, direct segment drive 10
Inverting common anode drive, direct segment drive 00

For the demo board, set uio[7:5] to 010

Press one of the buttons ui[6:0] (according to the selected button polarity) and release it. The dice roll is shown on the LED display for about 8 seconds.

  • ui[0] rolls a d4 (four sided die).
  • ui[1] rolls a d6
  • ui[2] rolls a d8
  • ui[3] rolls a d10
  • ui[4] rolls a d12
  • ui[5] rolls a d20
  • ui[6] rolls a d100

External hardware

Pullups on ui[6:0] with pushbuttons closing to GND.

A two-digit LED display. Common anode and/or cathode are supported using the configuraiton pins. Segments are connected to uo[7:0] (DP, G, F, E, D, C, B, A in that order) Left cathode connected to uio[1] Right cathode to uio[0]

Static configuration inputs on uio[7:5] should be connected to VDD or GND.

The chip may struggle to supply common anode displays with enough current. If so, drive the common anode pin with an inverting transistor driver and change the active level of the 'common' output by setting uio[7] to 0.

But wait: There's more!

The die roller only used 1/3 of the available area, and I had a few spare pins, so I also added a simple I2C slave to experiment with. It contains an 8 byte memory and a GPIO unit that can read the ui pins, and a GPIO pin uio[0] that can be used as input or output, and also has PWM capabilities.

The slave has a 7-bit I2C address 0x70. Communicate with it as if it were an I2C memory with a one byte address: Make a write transaction where the first byte is the sub-adress, followed by any number of data bytes. The data bytes will be stored in successive locations. Make a read transaction by first making a dummy write without data bytes to set the sub-address, followed by a restart and a read transaction to read any number of consecutive bytes back.

Address Map

The 7-bit I2C slave address is 0x70.

The address map of the peripheral is as follows:

Address Function
0x0 - 0x7 Memory cells
0x8 IOCtrl
0x9 IO_oe
0xA uio_in (r/o)
0xB ui_in (r/o)


Write 0 to set uio[0] to 0
Write 0 to 128 to output a PWM waveform with duty cycle IOCtrl/128
Write >128 to output 1


Bit 0 = 0 configures uio[0] as an input
Bit 0 = 1 configures uio[0] as an output

uio_in, ui_in

Reads the current values of the uio and ui pins.
Remember that the dice roller is still active, so you will see things happening on the uio[4:3] pins, as well as the state of the I2C pins.

Testing the I2C slave

Set the clock frequency to 10 MHz or above. It should be possible to access the I2C slave from the I2C1 interface of the RP2040 or from an I2C master connected to the PMOD interface J12, where you can also access he PWM output.


0Btn4segAPWM capable GPIO pin (bidir)
1Btn6segBSDA (bidir)
2Btn8segCSCL (input)
3Btn10segD1s digit common (output)
4Btn12segE10s digit common (output)
5Btn20segFButton polarity (input)
6Btn100segGSegment polarity (input)
7GPIO inputDPCommon polarity (input)

Chip location

Controller Mux Mux Mux Mux Mux Mux Mux Mux Mux Mux Mux Analog Mux Mux Mux Mux Mux Mux Mux Mux Mux Mux Mux Analog Mux Mux Mux Mux Mux Mux Mux Mux Mux Mux tt_um_chip_rom (Chip ROM) tt_um_factory_test (TinyTapeout 06 Factory Test) tt_um_analog_factory_test (TT06 Analog Factory Test) tt_um_analog_factory_test (TT06 Analog Factory Test) tt_um_urish_charge_pump (Dickson Charge Pump) tt_um_psychogenic_wowa (WoWA) tt_um_oscillating_bones (Oscillating Bones) tt_um_kevinwguan (Crossbar Array) tt_um_coloquinte_moosic (Moosic logic-locked design) tt_um_alexsegura_pong (Pong) tt_um_iron_violet_simon (Iron Violet) tt_um_tomkeddie_a (VGA Experiments in Tennis) tt_um_MichaelBell_tinyQV (TinyQV Risc-V SoC) tt_um_andychip1_sn74169 (sn74169) tt_um_mattvenn_r2r_dac (Analog 8bit R2R DAC) tt_um_thorkn_audiochip_v2 (AudioChip_V2) tt_um_faramire_gate_guesser (Gate Guesser) tt_um_urish_simon (Simon Says game) tt_um_TT06_SAR_wulffern (TT06 8-bit SAR ADC) tt_um_soundgen (soundgen) tt_um_ledcontroller_Gatsch (ledcontroller) tt_um_digitaler_filter_rathmayr (Digitaler Filter) tt_um_histefan_top (Snake Game) tt_um_mayrmichael_wave_generator (Wave Generator) tt_um_advanced_counter (jku-tt06-advanced-counter) tt_um_FanCTRL_DomnikBrandstetter (PI-Based Fan Controller) tt_um_ps2_morse_encoder_top (PS/2 Keyboard to Morse Code Encoder) tt_um_calculator_muehlbb (16-bit calculator) tt_um_hpretl_tt06_tempsens (Temperature Sensor NG) tt_um_haeuslermarkus_fir_filter (FIR Filter with adaptable coefficients) tt_um_mattvenn_rgb_mixer (RGB Mixer demo) tt_um_analog_loopback (Analog loopback) tt_um_entwurf_integrierter_schaltungen_hadner (Projekt KEIS Hadner Thomas) tt_um_seven_segment_fun1 (7-segment-FUN) tt_um_moving_average_master (Moving average filter) tt_um_rgbled_decoder (SPI to RGBLED Decoder/Driver) tt_um_4bit_cpu_with_fsm (4-Bit CPU mit FSM) tt_um_flappy_bird (Flappy Bird) tt_um_drops (drops) tt_um_enieman (UART-Programmable RISC-V 32I Core) tt_um_gabejessil_timer (2 Player Game) tt_um_wokwi_384804985843168257 (playwithnumbers) tt_um_wokwi_384711264596377601 (luckyCube) tt_um_hpretl_tt06_tdc (Synthesized Time-to-Digital Converter (TDC)) tt_um_wokwi_384437973887503361 (Asynchronous Down Counter) tt_um_spi_pwm_djuara (spi_pwm) tt_um_SteffenReith_PiMACTop (PiMAC) tt_um_mattvenn_relax_osc (Relaxation oscillator) tt_um_jv_sigdel (1st passive Sigma Delta ADC) tt_um_wokwi_392873974467527681 (PILIPINAS) tt_um_scorbetta_goa (GOA - grogu on ASIC) tt_um_sanojn_ttrpg_dice (TTRPG Dice + simple I2C peripheral) tt_um_urish_dffram (DFFRAM Example (128 bytes)) tt_um_lucaz97_monobit (Monobit Test) tt_um_noritsuna_i4004 (i4004 for TinyTapeout) tt_um_hpretl_tt06_tdc_v2 (Synthesized Time-to-Digital Converter (TDC) v2) tt_um_vaf_555_timer (A 555-Timer Clone for Tiny Tapeout 6) tt_um_obriensp_be8 (8-bit CPU with Debugger (Lite)) tt_um_toivoh_retro_console (Retro Console) tt_um_mattvenn_inverter (Double Inverter) tt_um_SteffenReith_ASGTop (ASG) tt_um_lucaz97_rng_tests (rng Test) tt_um_dieroller_nathangross1 (Die Roller) tt_um_kwilke_cdc_fifo (Clock Domain Crossing FIFO) tt_um_spiff42_exp_led_pwm (LED PWM controller) tt_um_devinatkin_fastreadout (Fast Readout Image Sensor Prototype) tt_um_ja1tye_tiny_cpu (Tiny 8-bit CPU) tt_um_7seg_animated (Animated 7-segment character display) tt_um_neurocore (Neurocore) tt_um_zhwa_rgb_mixer (RGB Mixer) tt_um_wokwi_394704587372210177 (Cambio de giro de motor CD) tt_um_ian_keypad_controller (Keypad controller) tt_um_urish_spell (SPELL) tt_um_vks_pll (PLL blocks) tt_um_fountaincoder_top (multimac) tt_um_dsatizabal_opamp (Simple FET OpAmp with Sky130.) tt_um_obriensp_be8_nomacro (8-bit CPU with Debugger) tt_um_LFSR_shivam (10-bit Linear feedback shift register) tt_um_shivam (Pulse Width Modulation) tt_um_algofoogle_tt06_grab_bag (TT06 Grab Bag) tt_um_meiniKi_tt06_fazyrv_exotiny (FazyRV-ExoTiny) tt_um_wokwi_394888799427677185 (4-bit stochastic multiplier traditional) tt_um_QIF_8bit (8 Bit Digital QIF) tt_um_MATTHIAS_M_PAL_TOP_WRAPPER (easy PAL) tt_um_andrewtron3000 (Rule 30 Engine!) tt_um_tommythorn_4b_cpu_v2 (Silly 4b CPU v2) tt_um_aerox2_jrb8_computer (The James Retro Byte 8 computer) tt_um_wokwi_394898807123828737 (4-bit Stochastic Multiplier Compact with Stochastic Resonator) tt_um_argunda_tiny_opamp (Tiny Opamp) tt_um_fdc_chip (Frequency to digital converters (asynchronous and synchronous)) tt_um_8bit_cpu (8-Bit CPU In a Week) tt_um_mitssdd (co processor for precision farming) tt_um_fstolzcode (Tiny Zuse) tt_um_liu3hao_rv32e_min_mcu (tt06-RV32E_MinMCU) tt_um_kianV_rv32ima_uLinux_SoC (KianV uLinux SoC) tt_um_wokwi_395444977868278785 (*NOT WORKING* HP 5082-7500 Decoder) tt_um_wokwi_394618582085551105 (Keypad Decoder) tt_um_wokwi_395054820631340033 (Workshop Hackaday Juli) tt_um_wokwi_395055035944909825 (Some_LEDs) tt_um_wokwi_395055351144787969 (Hack a day Tiny Tapeout project) tt_um_wokwi_395054823569451009 (First TT Project) tt_um_wokwi_395054823837887489 (Dice) tt_um_wokwi_395055341723330561 (Workshop_chip) tt_um_jduchniewicz_prng (8-bit PRNG) tt_um_wokwi_395054564978002945 (Bestagon LED matrix driver) tt_um_wokwi_395054466384583681 (1-Bit ALU 2) tt_um_wokwi_395058308283408385 (test for tiny tapeout hackaday) tt_um_s1pu11i_simple_nco (Simple NCO) tt_um_wokwi_395055359324730369 (Tiny_Tapeout_6_Frank) tt_um_disp1 (Display test 1) tt_um_pckys_game (PCKY´s Successive Approximation Game) tt_um_tiny_shader_mole99 (Tiny Shader) tt_um_wokwi_393815624518031361 (My Chip) tt_um_minibyte (Minibyte CPU) tt_um_emilian_rf_playground (IDAC8 based on divide current by 2) tt_um_triple_watchdog (Triple Watchdog) tt_um_wokwi_395142547244224513 (EFAB Demo 2) tt_um_chisel_hello_schoeberl (Chisel Hello World) tt_um_aiju_8080 (8080 CPU) tt_um_wokwi_395134712676183041 (Inverters) tt_um_nubcore_default_tape (DEFAULT) tt_um_wuehr1999_servotester (Servotester) tt_um_wokwi_395055722430895105 (Servo Signal Tester) tt_um_exai_izhikevich_neuron (Izhikevich Neuron) tt_um_lisa (LISA 8-Bit Microcontroller) tt_um_wokwi_394707429798790145 (32-Bit Galois Linear Feedback Shift Register) tt_um_CKPope_top (X/Y Controller) tt_um_MNSLab_BLDC (Universal Motor and Actuator Controller) tt_um_couchand_dual_deque (Dual Deque) tt_um_JamesTimothyMeech_inverter (Programmable Thing) tt_um_signed_unsigned_4x4_bit_multiplier (Signed Unsigned multiplyer) tt_um_lipsi_schoeberl (Lipsi: Probably the Smallest Processor in the World) tt_um_i_tree_batzolislefteris (Anomaly Detection using Isolation trees) tt_um_wokwi_394830069681034241 (Cyclic Redundancy Check 8 bit) tt_um_rng_3_lucaz97 (RNG3) tt_um_wokwi_395263962779770881 (Bivium-B Non-Linear Feedback Shift Register) tt_um_dvxf_dj8 (DJ8 8-bit CPU) tt_um_silicon_tinytapeout_lm07 (Digital Temperature Monitor) tt_um_htfab_flash_adc (Flash ADC) tt_um_chisel_pong (Chisel Pong) tt_um_wokwi_395414987024660481 (HELP for tinyTapeout) tt_um_jorgenkraghjakobsen_toi2s (SPDIF to I2S decoder) tt_um_cmerrill_pdm (Parallel / SPI modulation tester) tt_um_csit_luks (CSIT-Luks) tt_um_wokwi_395357890431011841 (Trivium Non-Linear Feedback Shift Register) tt_um_drburke3_top (SADdiff_v1) tt_um_cejmu_riscv (TinyRV1 CPU) tt_um_rejunity_current_cmp (Analog Current Comparator) tt_um_loco_choco (BF Processor) tt_um_qubitbytes_alive (It's Alive) tt_um_wokwi_395061443288867841 (BCD to single 7 segment display Converter) tt_um_SJ (SiliconJackets_Systolic_Array) tt_um_ejfogleman_smsdac (8-bit DEM R2R DAC) tt_um_wokwi_395055455727667201 (Hardware Trojan Part II) tt_um_ericsmi_weste_problem_4_11 (Measurement of CMOS VLSI Design Problem 4.11) tt_um_wokwi_395034561853515777 (2 bit Binary Calculator) tt_um_mw73_pmic (Power Management IC) tt_um_Counter_1_shivam (8-bit Binary Counter) tt_um_wokwi_395054508867644417 (SynchMux) tt_um_otp_encryptor (TT06 OTP Encryptor) tt_um_wokwi_395514572866576385 (Parity Generator) tt_um_ADPCM_COMPRESSOR (ADPCM Encoder Audio Compressor) tt_um_3515_sequenceDetector (Sequence detector using 7-segment) tt_um_faramire_stopwatch (Simple Stopwatch) tt_um_ks_pyamnihc (Karplus-Strong String Synthesis) tt_um_dlmiles_muldiv8 (MULDIV unit (8-bit signed/unsigned)) tt_um_dlmiles_muldiv8_sky130faha (MULDIV unit (8-bit signed/unsigned) with sky130 HA/FA cells) tt_um_tommythorn_ncl_lfsr (NCL LFSR) tt_um_lk_ans_top (ANS Encoder/Decoder) tt_um_MichaelBell_latch_mem (Latch RAM (64 bytes)) tt_um_wokwi_395179352683141121 (Combination Lock) tt_um_Uart_Transciver (UART Transceiver) tt_um_dgkaminski (4-Bit ALU) tt_um_DigitalClockTop (TDM Digital Clock) tt_um_wokwi_394640918790880257 (IFSC Keypad Locker) tt_um_wokwi_395355133883896833 (BIT COMPARATOR) tt_um_alu (SumLatchUART_System) tt_um_alfiero88_VCII (VCII) tt_um_ALU (3-bit ALU) tt_um_topTDC (Convertidor de Tiempo a Digital (TDC)) tt_um_UABCReloj (24 H Clock) tt_um_CDMA_Santiago (CDMA_2024) tt_um_dr_skyler_clock (Clock) tt_um_motor (motor a pasos) tt_um_mult_2b (mult_2b) tt_um_CodHex7seg (Decodificador binario a display 7 segmentos hexadecimal) tt_um_S2P (Serial to Parallel Register) tt_um_PWM (PWM) tt_um_ss_register (serie_serie_register) tt_um_stepper (Stepper) tt_um_g3f (Generador digital trifásico) tt_um_ALU_DECODERS (ALU with a Gray and Octal decoders) tt_um_ram (4 bit RAM) tt_um_sap_1 (SAP-1 Computer) tt_um_guitar_pedal (Integrated Distorion Pedal) tt_um_mbalestrini_usb_cdc_devices (Two ports USB CDC device) tt_um_adammaj (Tiny ALU) tt_um_wokwi_395567106413190145 (4-Bit Full Adder and Subtractor with Hardware Trojan) tt_um_gak25_8bit_cpu_ext (Most minimal extension of friend's 'CPU In a Week' in a day) tt_um_hsc_tdc (UCSC HW Systems Collective, TDC) tt_um_BoothMulti_hhrb98 (UACJ-MIE-Booth 4) tt_um_dlmiles_poc_fskmodem_hdlctrx (FSK Modem +HDLC +UART (PoC)) tt_um_simplez_rcoeurjoly (tt6-simplez) tt_um_nurirfansyah_alits01 (Analog Test Circuit ITS: VCO) tt_um_ppca (drEEm tEEm PPCA) tt_um_wokwi_395522292785089537 (Displays CIt) tt_um_fpu (Dgrid_FPU) tt_um_duk_lif (Leaky Integrate and fire neuron(LIF)) tt_um_bomba1 (Latin_bomba) tt_um_chatgpt_rsnn_paolaunisa (ChatGPT designed Recurrent Spiking Neural Network) tt_um_bit_ctrl (Bit Control) tt_um_array_multiplier_hhrb98 (Array Multiplier) tt_um_wallace_hhrb98 (UACJ-Wallace multiplier) tt_um_I2C_to_SPI (TinyTapeout SPI Master) tt_um_rng (Random number generator) tt_um_wokwi_395599496098067457 (EVEN AND ODD COUNTERS) tt_um_8bitALU (8bit ALU) tt_um_aleena (Analog Sigmoid) tt_um_rejunity_1_58bit (Ternary 1.58-bit x 8-bit matrix multiplier) tt_um_rejunity_fp4_mul_i8 (FP4 x 8-bit matrix multiplier) tt_um_PWM_Controller (PWM Controller) tt_um_couchand_cora16 (CORA-16) tt_um_frq_divider (clk frequency divider controled by rom) tt_um_wokwi_390913889347409921 (Notre Dame Dorms LED) tt_um_timer_counter_UGM (4-Digit Scanning Digital Timer Counter) tt_um_koconnor_kstep (kstep) tt_um_lancemitrex (DIP Switch to HEX 7-segment Display) tt_um_PWM_Sine_UART (PWM_Sinewave_UART) tt_um_nicklausthompson_twi_monitor (TWI Monitor) tt_um_wokwi_395615790979120129 (Cambio de giro de motor CD) tt_um_ancho (Circuito PWM con ciclo de trabajo configurable) tt_um_wokwi_395618714068432897 (32b Fibonacci Original) tt_um_voting_thingey (Voting thingey) tt_um_hsc_tdc_buf (UCSC HW Systems Collective, TDC - BUF2x1) tt_um_hsc_tdc_mux (UCSC HW Systems Collective, TDC - MUX2x1) tt_um_petersn_micro1 (14 Hour Simple Computer) tt_um_sanojn_tlv2556_interface (UART interface to ADC TLV2556 (VHDL Test)) tt_um_gray_sobel (Gray scale and Sobel filter) tt_um_wokwi_395614106833794049 (Universal gates) Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available